Composite product including magnetic material and method of production thereof

ABSTRACT

Method of producing a composite product, including providing within a mold cavity at least two dissimilar powders so that one of such powders adheres to part of or the entire surface that defines the cavity. At least one of the powders can be magnetic, so that the magnetic powder is provided in the cavity under the influence of a magnetic field to locate the magnetic powder at a predetermined position in the cavity in response to the field, another powder being provided in the remainder of the mold cavity, after which the powders are consolidated into a selfsustaining body that can be sintered. The magnetic powder can be a material susceptible to magnetic attraction, such as nickel, iron and/or cobalt, or the individual particles thereof can have an exterior or interior portion of such magnetic material.

United States Patent [191 Butcher et al.

[ COMPOSITE PRODUCT INCLUDING MAGNETIC MATERIAL AND L'IETI-IOD OFPRODUCTION THEREOF [75] Inventors: John William Butcher, Solihull;

Timothy John Thexton, Birmingham, both of England [73] Assignee: TheInternational Nickel Company,

Inc., New York, N.Y.

22 Filed: Nov. 18,1971

211 Appl. No.: 200,200

[52] US. Cl. 29/182.2, 75/208 R, 75/211, 75/214, 75/200, 29/1823,29/182, 148/103, 148/108 [51] Int. Cl. B22f 1/00, B22f 3/00, 1322f 7/00[58] Field of Search 75/208, 214, 211, 200; 29/182, 182.2, 182.3;148/103, 108

[56] References Cited UNITED STATES PATENTS 3,161,504 12/1964 Black eta1 75/208 2,384,215 9/1945 Toulmin, Jr. 75/226 3,359,622 l2/1967 Meyeret a1... 75/208 2,192,743 3/1940 Howe 75/208 3,428,498 2/1969 Heimke148/103 Apr. 30, 1974 2,148,040 2/1939 Schwarzkopf 75/226 FOREIGNPATENTS OR APPLICATIONS 1,067,539 10/1959 Germany 75/214 PrimaryExaminerBenjamin R. Padgett Assistant Examiner-B. Hunt ABSTRACT Methodof producing a composite product, including providing within a moldcavity at least two dissimilar powders so that one of such powdersadheres to part of or the entire surface that defines the cavity. Atleast one of the powders can be magnetic, so that the magnetic powder isprovided in the cavity under the influence of a magnetic field to locatethe magnetic powder at a predetermined position in the cavity inresponse to the field, another powder being provided in the remainder ofthe mold cavity, after which the powders are consolidated into aself-sustaining body that can be sintered. The magnetic powder can be amaterial susceptible to magnetic attraction, such as nickel, iron and/orcobalt, or the individual particles thereof can have an exterior orinterior portion of such magnetic material.

9 Claims, No Drawings COMPOSITE PRODUCT INCLUDING MAGNETIC MATERIAL ANDMETHOD OF PRODUCTION THEREOF The present invention relates to a methodof producing a composite powder metallurgy product and to the productmade thereby and more particularly to such a product that includes amagnetically attractable material.

Powder metallurgy processes may be employed in making composite articlesfrom two separate powders, in which articles the portion thereofcorresponding to one powder wholly or partly surrounds the portioncorresponding to the other powder. Normally such articles are circularor cylindrical and are usually hollow, an example being a bearingbushing that includes a first pair of one material with an interior orexterior lining of another material. Another example is a piston ringthat includes an interior part of one material with a facing or anothermaterial. In producing such articles from two powders, there isconsiderable difficulty in providing the two powder masses, one adjacentto the other, in a mold in which the powders are to be consolidated,e.g., by pressure compaction, such that there is no extensiveintermingling of the particles of the respective powders. The samedifficulty arises if, for example, one powder material is to line arecess in a body made from another powder.

It has now been discovered that a special powder metallurgy processenables the production of a composite product from a magnetic powder anda nonmagnetic powder so that a surface-defining portion of the productis substantially or completely composed of magnetic powder. This specialprocess also enables the production of a composite product from at leasttwo powder components with substantially no intermingling of the initialpowder components in the mold cavity before consolidation thereof.

It is, therefore, an object of the present invention to provide a methodof producing an integral composite body, a surface-defining portion ofwhich comprises a magnetic material, and overlies a second portionthereof of another metallic material.

Another object of the invention is to provide a method of producing acomposite body by consolidating a powder charge including at least twodissimilar powders with minimal intermingling of the respectiveparticles thereof.

Other objects and advantages will become apparent from the followingdescription.

Generally speaking, the present invention is directed to a method ofproducing a composite article from a plurality of powders, including thestep of disposing at least two powders of different composition in amold cavity so that one of these powders adheres to a part of or theentire cavity-defining surface, such adherence being achieved by a filmdisposed on the surface or by a magnetic field. In a preferredembodiment one of the powders (referred to herein as the magneticpowder) comprises magnetic material, and another one thereof comprises adissimilar material, the magnetic powder being provided in a mold cavityunder the influence of a magnetic field so that magnetic powder is moreconcentrated (i.e., the proportion thereof significantly exceeds theaverage proportion of the magnetic powder in the total powder charge inthe mold cavity) at a portion or portions of the mold cavitypredetermined by the magnetic field and the remainder of the mold cavityis filled substantially with other, e.g., non-magnetic, powder. Anon-magnetic powder can be introduced into the cavity concurrently withthe magnetic powder, the magnetic field preferentially attracting themagnetic powder so that it is more concentrated at the predeterminedportion or portions of the mold cavity, the non-magnetic powder beingmore concentrated at other portions of the mold cavity.

Alternatively, the magnetic powder can be introduced first in the moldcavity under the influence of the magnetic field provided by magneticmeans and the second powder introduced thereafter so that the powdersare substantially completely segregated, the contact therebetweengenerally being limited to the interface of the powders, and themagnetic powder is substantially concentrated in the cavity regionadjacent to the magnetic means.

The powders in the cavity are then consolidated to produce aself-sustaining powder metallurgy product that is sinterable in standardfashion having regard for the melting points of the metals involved. Thepowder consolidation can be achieved by, for example, mechanical orisostatic pressing or mold sintering.

Generally, the powders employable in the present invention can have aparticle size of about 0.5 microns to about 200 microns, and preferablyrange in size from about 3 to 100 microns. The magnetic powder canconsist essentially of a magnetic material (i.e., one that isattractable by a magnet), such as a ferro-magnetic metal; for example,nickel, iron, cobalt, or mixtures or alloys thereof. Alternatively, themagnetic powder can comprise particles made of two or more componentparts, one of which parts is of magnetic material and the other of whichis of non-magnetic material, such as graphite, for example.Conveniently, non-magnetic materials such as graphite, alumina or otherrefractory oxides, refractory carbides or non-magnetic metals can becoated, in whole or in part, with a magnetic metal such as nickel, ironor cobalt. Such coating with the magnetic material can be achieved byvarious techniques, such as vapor deposition, chemical precipitation,electroless deposition, etc.

The quantity of magnetic material in the coated particles should besufficient to allow the ready attraction thereof by a magnet. Forexample, the magnetic material component can constitute, on the average,about 5 to about weight per cent, and, more preferably, about 20 toabout 60 weight per cent, of a coated particle. Non-magnetic powdermaterials that can be used as such in the invention include aluminum,copper, tantalum, columbium, tungsten, molybdenum and metal carbides.

Preferably, the magnet is a permanent magnet, such as, for example, asimple bar magnet. Because the magnetic lines of force concentrate atthe ends of the magnet, a greater deposit or concentration of magneticpowder will result at the ends than at other areas of the magnet. Themagnet can be laminated, e.g., comprised of two or more magnets arrangedend to end so that the overall field is made more uniform along itslength. A glass-ceramic magnet in which magnetic iron particles areadmixed and dispersed within the glass may be used in certain instances,particularly if a specific field pattern obtainable by suitabledistribution of the iron particles is desirable. The magnet may even bea temporary magnet, such as an electro-magnet, or a simple magnetproduced by induction.

The magnet can have a shape such that it constitutes part of or theentire side wall defining the mold cavity. The magnetic member can be asingle piece or include two or more mating parts.

More specifically, in one embodiment, magnetic powder is first providedon a magnetic member that is insertable into the mold cavity and thenthe magnetic member, with the magnetic powder thereon, is disposed inthe mold cavity. With the magnetic member and the magnetic powder in themold cavity, the other powder is poured into the cavity and then thepowder mass is consolidated. Alternatively, the magnetic member can beintroduced into the mold cavity and the magnetic powder can then beprovided on the magnetic member, as by dusting, for example, after whichthe other powder is provided in the cavity and the powders consolidated.

The invention is particularly applicable to the production of annularbodies, such as bearings, cylinders or bushings. For example, thepresent invention allows the production of a bushing or a sleeve ofaluminum with a lining of graphite. Of course neither aluminum norgraphite is magnetic, but one of these components, e.g., the graphitepowder, can be coated with a magnetic material, preferably nickel, sothat it is easily at tracted by a magnet. The graphite particle size canbe about 0.5 microns to about 200 microns and the nickel coatingthickness can be about 0.1 microns to about 5.0 microns. in themanufacture of such product the preferred steps are the provision of anon-magnetic cylindrical mold open at both ends, insertion into thelower end of the mold of an annular ring which forms the base of themold cavity, insertion into the opening in the ring of a cylindricalmagnet, coating of this magnet with the nickel-coated graphite powder toform a thin layer thereon, filling of the remaining annular cavity withaluminum powder, compression of the powder into a self-sustaining body,as by mechanical compaction, for example, and separation of the magnetfrom the resulting compacted body. The self-sustaining body can then besintered according to known techniques, e.g., in hydrogen at atemperature of about 550C to about 650C. Generally, such an annularsintered product will include a first (i.e., inner) part of graphiteparticles embedded within a matrix of the magnetic material (e.g.,nickel) and a physically distinct (i.e., outer) part of aluminum that isradially removed from the first part, these parts generally beingconcentric.

The nickel-coated graphite powder may be, for example, about 3 micronsin particle size and the aluminum powder may be of particle size such asto pass through a IOO-mesh BSS sieve. Typical dimensions of the mold,which may be of any appropriate nonmagnetic material, such as anickel-chromium-cobalt alloy, are an outside diameter of 2 inches, aninside diameter of l l/l6ths inch and a height of 2% inches. The magnetmay be of A-inch diameter and made, for example, of magnetized chromiumsteel. Where it is desired, the consolidated powder product may haveinterior and exterior surfaces of the same material (i.e., the magneticpowder material) and an interior of a nonmagnetic material. Of course,the consolidated powder product can be made so that the graphiteparticles embedded in the magnetic metal matrix form an outer partthereof with the aluminum forming an inner part.

The magnetic powder can easily be formed into a powder layer of aboutone-sixteenth inch thick simply by sprinkling it around the cylindricalmagnet while this is in the mold. An advantage obtained is that thepowder tends to become concentrated close to the poles of the magnet,that is to say at each end when a simple bar magnet is used, so that inthe resultant bearing bushing, the lining extends radially outwards overthe aluminum body at each end. Alternatively, the cylindrical magnet maybe coated before it is inserted in the mold cavity, as, for example, byrolling it over powder spread out on a horizontal surface, after whichthe thus-coated magnet is inserted in the mold.

If an article, such as a piston ring, requiring an external facing of amaterial such as graphite is being made, an annular magnet can be used,the method involving coating the inner surface of the annular magnetwith the magnetic powder, e.g., nickel-coated graphite, and providing asecond powder, e.g., aluminum, to the remainder of the mold cavity, andthen consolidating the powders.

A particular advantage obtained with the invention is that the magneticpowder can be substantially localized and not extensively mixed with theother powder, with the consequence that the strength of the aluminum orother body of the compact is not reduced.

While the attraction of more powder to the ends of a simple permanentmagnet than over the central length when the powder is applied bysprinkling or by rolling the magnet over powder spread on a horizontalsurface, gives some advantage where it is desired that in the resultingarticle the lining extends radially outwards over the body at each end,the uneven distribution becomes too pronounced generally and, therefore,disadvantageous when the resulting article is more than about 12 mm. inaxial length. Such a disadvantage can be overcome in another way ofcarrying out the invention, where the first powder is caused to adhereto a film of a suitable liquid on a part of or the entire cavitydefiningsurface of the mold, thereby providing a thin layer of such powder. Thisfilm material must wet the cavity-defining surface and can be tacky, butthis material need not be an adhesive as that term is commonlyunderstood. A particularly suitable such liquid is a silicone material,e.g., hexamethyldisiloxane, which can also act as a lubricant infacilitating the removal of the compact from the mold. After forming thethin layer of powder on the film, the second powder can be poured intothe cavity. Of course, when the invention is carried out in this way thelining or facing powder need not be magnetic and may for example be amixture or composite of metal powder and graphite, but in forming a thinlubricating layer nickel-coated graphite is still very suitable, sincethe nickel improves the strength and wearresistance of the lubricatinglayer and causes it to adhere to the lubricant-free bulk of the bearing.Moreover, the only limit on the axial length of the compact is imposedby the practical difficulties in filling a long mold and compacting thepowder in it.

The thickness of the layer of the lining or coating powder formed on thefilm depends largely on the particle size of the powder. Where thepowder is 3 microns in average particle size and the object is toprovide a very thin lubricating facing or lining, the powder layer canbe about 5 microns thick. The invention is particularly useful in theprovision of facing or lining layers of up to about 10 or more micronsthick; however, thicker 3,807,966 6 layers are easily formed,particularly with the use of up as a coating by the magnet depends uponits flowmagnetic field or by the alternate formation of films ofability, but even nickel powder, which does not flow material to whichpowders can adhere and layers of fr ly, an be used,

powder par icle adh r ng to e films, P even with The concurrentprovision of the various powders to large powder particles the maximumthickness of e 5 the mold cavity in accordance with the presentinvenpowder layer generally is about 200 micron tion permits the use ofa single automatic feeding dean example a f y of carrying the inventionvice and a single cavity-filling operation, thereby prowith the use of aliquid film a composite product was viding cost savings m 9 a mold {madeof die Steel w h had an Although the present invention has beendescribed in side diameter of 3 inches and an inside diameter of 1 l0conjunction with preferred embodiments it is to be Inch, and wasProvlded a "h dlah'feter e derstood that modifications and variationsmay be rered the lower end of which fitted mm wheh sorted to withoutdeparting from the spirit and scope of formed the base of the mold Thecore Ted was the invention as those skilled in the art will readilyunsprayed with a Solution of hexamethyldishoxane derstand. Suchmodifications and variations are considcone m acetone. to a fi on Itssurfaceland the ered to be within the purview and scope of the invencorerod then dipped mto nickel-coated graphite powtron and appended claims.der. Approximately 0.13 gms. of powder adhered to the we claim: coresurface. The coated core rod was then inserted in 1. A sintered powdermetallurgy product comprising 2; ggligfi g ggg i ig g a i i gfig gfr gga relatively wear-resistant facing of about 5 to about poured into theannular cavity and the powders were 200 mlcrops thickness e graphitepamcles then compacted under a pressdre of 15 tonflin When embeddeqm a Fmamx of metal Characterized the annular compact was separated from themold and by being atirached by a magnet a core all the nickel-coatedgraphite adhered to its interbeckmg a i material dlfieeliem from the pnal surface. The compact was then sintered to a final Sand f' bemg.nter'bonded dlrecfly to the facmg product useful as a bearing andcontaining a ma or proportion of a metal from the group consisting ofaluminum and copper.

In place of aluminum, the body of a bearing having 2 A a. surface layerformed from nickel-coated graphite powfier metanlfrgy product. defined mclaim 1, wherein the matrix metal consists esmay consist of other metalsor alloys, for example alloys of copper with in, 6%, 5%Sn 95% Cu or 10%sentlally of at least one of "On, nickel and cobalt.

Sn 90% Cu; copper with lead and phosphorus; and composne powfiermetahurgy prodlfct as iron with copper. Such alloys may conveniently befihed m F wherem the male Propomoh of the formed by the use of thefollowing powder mixtures to hackmg aluminumform the body of the bearing7 4. A composite powder metallurgy product as de- 25 Cu 75 Fe 6.0

The magnetic field can be generated within the cavity 4 fined in claim 1wherein the major proportion of the by means of, for example, the lowerpunch of a mebacking is copper. chanical powder press, which punch canbe a perma- 5. A composite powder metallurgy product as denent magnet.Alternatively, the lo er punch a be fined in claim 1 wherein the facingcomprises nickelused as the core of an electromagnet, for example, incoated graphite particles. which case the punch is magnetized before thepowders A powder metallurgical method of producing a are P h fhautemat'c e composite body with at least a portion of the surface feedmgshoe can be e to feed a thereof differing substantially in compositionfrom the ture of the magnetic and non-magnetic powders to the remainderof Said body comprising. cavity. The powder material distributionpresent in the mold cavity is carried over to the sintered product so amold ef at lees? that the product includes a greater concentration ofhavfhg dlsshmlaf eomposmohs and f magnetic powder material atsurface-defining portions h eharaeter'sheer at least one of Sam Powdersthereof and a higher proportion of non-magnetic po g more gneticallyattractable than an ther der material in the other portions. It is notedthat theof Said Powdersr f the under the lhflu' portions ofthewsvintgred Product includinglnggqetig ence of a magnetic field thatpreferentially attracts and moves the more magnetic powder toward anpowder in greater concentration can al so inelude small i mterrorsurface of the cavity to thereby provide a concentration of the magneticpowder at a predeamounts of the non-magnetic material.

A sintered product made in the above manner can be used as a seal for arotor of a rotary internal combuslh s rf ce P elheh. YYlPhlSi' aY L tand tion engine, for example, where the magnetic powder b. consolidatingsaid powders, while maintaining said comprises nickel-coated graphiteand the second powconcentration of magnetic powder at the predeterdercomprises aluminum. mined surface position, to produce a self-sustainingNaturally, the ease with which the powder is picked body having asurface portion differing substan- 7 tially in composition from theremainder of the body. 7

7. A method of producing a composite body as defined in claim 6, whereinsaid powders are introduced concurrently into said cavity.

8. A process as set forth in claim 6 wherein the more magneticallyattractable powder is introduced into the mold cavity and ismagnetically moved to the predetermined surface position within thecavity prior to the introduction of another powder into the mold cavity.

9. A powder metallurgical process using two different powders formanufacture of a compacted powder metallurgical product having one ofthe powders in a surface layer portion bonded to a second portioncontaining the second powder, wherein the first powder is a magneticallyattractable material and is of a chemical composition different from thechemical composition of the second powder, comprising:

a. magnetically attracting and moving particles of the first powder intoclose proximity with a mold cavity wall to provide a layer of the firstpowder at said cavity wall;

b magnetically maintaining the layer of the first powder at said cavitywall;

c. introducing the second powder into the mold cavity and disposing thesecond powder against the first powder layer while maintaining the firstpowder in close proximity with said cavity wall and segregated from thesecond powder;

d. compacting the two powders together under pressure sufficient toproduce a self-sustaining powder metallurgical product; and

e. ejecting the compacted product to obtain a selfsustaining powdermetallurgical product having a surface layer portion that differssubstantially in composition from the other portion of the product.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO.3,807,966

DATED April 30, 1974 INVENTOR(S) John William Butcher and Timothy JohnThexton It is certified that error appears in the aboveidentified patentand that said Letters Patent are hereby corrected as shown below:

Front page should read at left hand column:

[30] Foreign Application Priority Data 11/26/70 GreatBritain 56269/7011/ 3/71 Great Britain 5l2ILl/7l Col, 1, line 16, for "pair" read "part-Line 20, for "or" read "of",

Signed and Sealed this ninth Day of September 1975 [SEAL] A ttes r.-

RUTH C. MASON C. MARSHALL DANN Alluring Officer (mmnissimu'r uj'larenrsand Trademarks

2. A composite powder metallurgy product as defined in claim 1, whereinthe matrix metal consists essentially of at least one of iron, nickeland cobalt.
 3. A composite powder metallurgy product as defined in claim1 wherein the major proportion of the backing is aluminum.
 4. Acomposite powder metallurgy product as defined in claim 1 wherein themajor proportion of the backing is copper.
 5. A composite powdermetallurgy product as defined in claim 1 wherein the facing comprisesnickel-coated graphite particles.
 6. A powder metallurgical method ofproducing a composite body with at least a portion of the surfacethereof differing substantially in composition from the remainder ofsaid body, comprising: a. introducing into a mold cavity at least twopowders having dissimilar compositions and dissimilar magneticcharacteristics, at least one of said powders being more magneticallyattractable than another of said powders, while the cavity is under theinfluence of a magnetic field that preferentially attracts and moves themore magnetic powder toward an interior surface of the cavity to therebyprovide a concentration of the magnetic powder at a predeterminedsurface position within said cavity, and b. consolidating said powders,while maintaining said concentration of magnetic powder at thepredetermined surface position, to produce a self-sustaining body havinga surface portion differing substantially in composition from theremainder of the body.
 7. A method of producing a composite body asdefined in claim 6, wherein said powders are introduced concurrentlyinto said cavity.
 8. A process as set forth in claim 6 wherein the moremagnetically attractable powder is introduced into the mold cavity andis magnetically moved to the predetermined surface position within thecavity prior to the introduction of another powder into the mold cavity.9. A powder metallurgical process using two different powders formanufacture of a compacted powder metallurgical product having one ofthe powders in a surface layer portion bonded to a second portioncontaining the second powder, wherein the first powder is a magneticallyattractable material and is of a chemical composition different from thechemical composition of the second powder, comprising: a. magneticallyattracting and moving particles of the first powder into close proximitywith a mold cavity wall to provide a layer of the first powder at saidcavity wall; b. magnetically maintaining the layer of the first powderat said cavity wall; c. introducing the second powder into the moldcavity and disposing the second powder against the first powder layerwhile maintaining the first powder in close proximity with said cavitywall and segregated from the second powder; d. compacting the twopowders together under pressure sufficient to produce a self-sustainingpowder metallurgical product; and e. ejecting the compacted product toobtain a self-sustaining powder metallurgical product having a surfacelayer portion that differs substantially in composition from the otherportion of the product.